We have done both caravan (with family) moved on to coachbuilt motorhome, (again with family) and now gone back to caravan (no family anymore). There are advantages and disadvantages with both but the main factors influencing our recent choice were:
1. Cost
The cost of a motorhome is very high and we were not prepared to use all our savings in that direction. We also already had a suitable tow vehicle. In addition you may need to buy a car as a runabout and this will add to the costs again. It is argued that depreciation of a motorhome is lower than a car, and this is true. But in percentage terms of the amount of money you will need to handover to make an exchange for a new vehicle, there is little difference. You are just working much larger numbers with motorhomes.
2. Space
There is far more free space in a caravan as motorhomes have to take into account the cab. They are also trying these days to cram too much equipment into the available space and you can often just end up with a small passage down the middle. Both caravans and motorhomes can be fitted with spacious awnings which does help, especially in the sunnier climes. Bed sizes are usually bigger in caravans for the same reasons.
3. Fuel & Toll Costs.
This is more applicable in Europe. Yes the diesel in Europe is much cheaper than here but this is usually only in supermarkets. These are starting to fit very narrow access lanes, and even height barriers so coachbuilts can often be excluded, although they are not the primary target. In additon many motorhomes are only getting mid 20's for fuel consumption. Many tuggers wil claim at least that using diesel cars. Motorhomes also get penalised on French Toll roads as a Class 3 vehicle. Caravans are only Class 2.
At the end of the day it is a factor of your lifestyle and of course, your own choice.